1. Field of the Invention
The invention concerns the field of heat brakes for bending thermoplastic sheets clad ducts for HVAC applications, and to methods and machines for producing clad ducts.
2. Description of the State of the Art
During a search for patents related to the present invention, published U.S. Patent application Nos. 20110030833 and 20060083889 were noted. In addition, the following were noted U.S. Pat. Nos. 7,712,787, 6,763,853, 6,716,520, 6,360,783, 5,944,060, 5,918,644, 3,251,382, 3,212,529, and 1,916,908.
The integrity of ductwork is a major concern for the HVAC industry and also for building owners. When the integrity of ductwork is compromised, the consequences range from increased energy costs to contamination of air supplied to a building. The integrity of outdoor ductwork is of particular concern because it is exposed to the elements and must withstand much harsher conditions than indoor ductwork. For decades, outdoor ductwork has been clad with sheet metal to protect it from the elements but the results have been disappointing. Corrosion, leaks and contamination have plagued outdoor ductwork clad with sheet metal. There is a tremendous need for clad ductwork that has good R value and that will maintain its integrity for extended periods of time, especially outdoors. In meeting this need, consideration must be given to many things including manufacturing costs, installation costs, performance, and durability.
It is an object of the invention to provide a heat brake especially suited for heating a sheet of thermoplastic material.
It is a further object of the invention to provide a heat brake especially suited for producing a clad duct from a laminate comprising a sheet of thermoplastic material bonded to a sheet of foam.
It is a further object of the invention to provide a heat brake with a plenum operable to maintain a negative pressure for drawing cooling air through a slot in a split work support table.
It is a further object of the invention to provide a heat brake with a second plenum that can be selectively pressurized to direct heating air towards a specific portion of a thermoplastic sheet.
It is a further object of the invention to provide a heat brake that is operable to sequentially heat portions of a thermoplastic sheet in rapid succession.
These and other objects and advantages of the present invention shall be apparent from the following detailed description with reference, therein, to the several drawing figures.